A maid began opening the upper windows of his house, appeared momentarily in each, and, leaning from a large central bay, spat meditatively into the garden.

This disrespectful gesture is emblematic of the way people treat Gatsby — they live off his largesse and suck up to him in public, but in moments away from his gaze, they handle themselves crassly.

It also contrasts reality with appearance in that Gatsby’s lavish mansion seems absolutely perfect. But in the end, it’s still full of people who aren't— reality is grittier than superficial appearance.